11. Congress has always opened with a prayer and the practice has been upheld by the SCOTUS

Doesn't mean that I agree with the SCOTUS decision, but the question of "what happened to the Constitution" suggests that there has been some sort of recent change in practice. In fact , the same Congress that approved the language of the First Amendment also almost simultaneously approved legislation appropriating funds for the appointment of a paid chaplain whose duties included, among other things, giving an opening prayer at sessions of Congress.